Sliding contact material, clad compoosite material, commutator employing said material and direct current motor employing said commutator

ABSTRACT

Sliding contacts comprising alloys such as Pd/Cu/Ag, Pt/Cu/Ag, Pd/Cu/Ag/Ni, Pt/Cu/Ag/Ni, Ag/Pd/Cu,Au, Ag/Pt/Cu/Au and two-layered composites comprising a surface layer of one of the foregoing alloys and a base layer comprised of copper or a copper-containing alloy. Also, three-layered composites comprising a surface layer of one of the foregoing alloys, an intermediate layer of one of the foregoing alloys and a base layer comprised of copper or a copper-containing alloy as well as direct current motors comprising commutators comprising a three-layered composite.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is an application which has been filed under 35 U.S.C.§371 from parent International Application No. PCT/JP96/00409 having aninternational filing date of 23 Feb. 1996.

BACKGROUND OF THE INVENTION

The present invention relates to contact material employed for anelectrically and mechanically sliding portion, and more specifically tothe contact material and clad composition material containing thecontact material which may be employed in a commutator equipped in adirect current motor, especially in a direct current compact motor,having a sufficiently long life and a low starting voltage when it isemployed for the material of a compact disk spindle.

In recent years, the number of apparatuses in which sliding contactoccurs has been increased in the field of electronic industries so thatthe development of new sliding contact material and the researchregarding abrasion have been extensively conducted. The abrasion and thecontact resistance are problematic in the sliding contact material, butthis abrasion phenomenon is complex so that there are many aspectsacademically unelucidated.

Even though the metal surface of the contact material is intended to befinished relatively smoothly, the microscopic observation reveals thatthe surface is not a completely flat surface but ordinarily possessesminute unevenness. Although two metal surfaces appear to be in contactwith each other with a large contact area, they are actually in contactwith each other only with isolated projections due to the existence ofthe several concaves and convexes.

The abrasion due to the friction is basically proportional to thestrength of a contact force and inversely proportional to the hardness.A temperature, a humidity, a corrosive component, organic vapor, dustand the like are factors introducing a change in the abrasion andelectrical performances (contact resistance).

The wear in the sliding contact material is largely divided intoadhesive wear and abrasion wear. The adhesive wear takes place by meansof the welding between the metals of the actual contact potions or theprojections so as to tear off the softer metal which is shifted to theharder metal.

The abrasion wear is induced when two groups of material having largelydifferent hardnesses are rubbed with each other or when two groups ofsoft material one of which contains hard particles are rubbed.

The sliding contact material is widely utilized for an earth ring, arotary switch and other devices inclusion a direct current compact motorfor a compact disk spindle and a commutator employed in the directcurrent compact motor. Three-layered clad composite material employed asa conventional commutator for a compact disk spindle of a direct currentcompact motor is known to consist of a surface layer composed of anAu--Ag alloy consisting of 40% in weight of Ag and a balance of Au, anintermediate layer composed of an Ag--Cu--Ni alloy consisting of 4% inweight of Cu. 0.5% in weight of Ni and a balance of Ag and a base layercomposed of a Cu--Sn--Ni alloy consisting of 9.5% in weight of Ni, 2.5%in weight of Sn and a balance of Cu.

Another pertinent prior reference discloses a rectifier having as acommutator an Ag--Pd--Cu alloy essentially consisting of 2 to 10% inweight of Cu, 2 to 10% weight of Pd and a balance of Ag. However, inthis rectifier, the improvements on the performances, especially under ahigh temperature circumstance, such as the increase of a contactresistance and instabilities generated by black powder produced due toPd and the generation of an electrical noise have been requested.

With the miniaturization of audio devices in the recent years, thedirect current compact motor is equipped near a heating element such asan amplifier so that the temperature of the motor even at normaloperation condition may reach to 70° C. Especially when the motor isequipped in an automobile, the temperature under the midsummer burningsun may reach over 70° C.

Generally, the life of the direct current compact motor equipped with abrush under the high temperature circumstance is unexpectedly short.While the above motor has a life of about 6000 hours under acircumstance of a temperature of 25° C. and a humidity of 60%, its lifemay be reduced to about 200 hours under a circumstance of a temperatureof 70° C. and a humidity of 5%.

Accordingly, the development of a direct current compact motor whichdoes not lose the durability under the high temperature has beendemanded.

As a result of detailed investigation of the reasons why the life isreduced, it has been clarified that the commutator material is scrapedoff by means of a brush at the time of sliding between the commutatorand the brush under a high temperature circumstance, which is depositedon the brush surface to form projection-like sediment, and theprojection acts as if it were a blade to scrape off the commutatormaterial long and narrow.

The long and narrow needle-like powder thus produced fills the spacesamong the divided cylindrical commutator to short-circuit andelectrically conduct the divided commutators so as to result in thestopping of the motor.

Even if the electrical conduction does not occur, the abrasion rateunder the above high temperature condition is larger than that of thecondition of a temperature of 25° C. and a humidity of 60%, and thescraping-off of almost all the motors reaches to the Cu alloy of thebase layer in 500 hours not only to increase the contact resistance butalso to hinder the conduction by means of CuO derived from the exposedCu so that the motor functionally stops.

SUMMARY OF THE INVENTION

An object of the present invention is to provide sliding contactmaterial which possesses durability over a relatively long period oftime.

Another object of the present invention is to provide clad compositematerial containing the said sliding contact material.

A further object of the present invention is to provide a commutatorcontaining the clad composite material.

A still further object of the present invention is to provide a directcurrent motor containing the said commutator having a life over 2000hours over a wide temperature range between 30° and 70° C.

A still further object of the present invention is to provide a directcurrent compact motor employed for a compact disk spindle.

The present invention may provide the below eight alloys employed forsliding contact material of an electrically and mechanically slidingportion of a sliding contact (all numerals are % in weight).

1 Ag(10 to 60)-Cu(0.1 to 7)-Au (balance)

2 Ag(10 to 60)-Pd(0.1 to 7)-Cu (0.1 to 7)-Au (balance

3 Ag(10 to 60)-Pt(0.1 to 7)-Cu (0.1 to 7)-Au (balance

4 Cu(5 to 10)-Ni (0.1 to 1)-Ag (balance)

5 Pd(0.1 to 1.5)-Cu (3 to 10)-Ag (balance)

6 Pd(0.1 to 1.5)-Cu (3 to 10)-Ni (0.1 to 1)-Ag (balance)

7 Pt(0.1 to 1.5)-Cu (3 to 10)-Ag (balance)

8 Pt(0.1 to 1.5)-Cu (3 to 10)-Ni (0.1 to 1)-Ag (balance)

The present invention also provides two-layered clad composite materialwhich comprises a surface layer composed of the above sliding contactmaterial 1 to 8 and a base layer composed of Cu or a Cu alloy.

The present invention also provides three-layered clad compositematerial which comprises a surface layer composed of the above slidingcontact material 1 to 8, an intermediate layer composed of the abovesliding contact material 1 to 8 and a base layer composed of Cu or a Cualloy.

The present invention also provides a commutator which comprises theabove clad composition material having the above sliding contactmaterial 1 to 8.

The present invention also provides a direct current motor whichcomprises the above commutator.

The above Cu alloy employed as a base layer includes phosphor bronze(CuSnNi alloy). German silver (CuZnNi alloy) and other conventionalalloys.

In accordance with the present invention, the deposition of the scrapedmaterial to the brush and the resulting generation of the needle-likeabrasion power are depressed maintaining the conventional low startingvoltage by adding Cu or, Pd or Pt to the AuAg alloy of the surface layerof the three-layered clad composite material.

The deposition of the scraped material to the brush and the resultinggeneration of the needle-like abrasion powder are also depressed byincreasing the amount of Cu in the AgCu alloy or the AgCuNi alloy of theintermediate layer of the three-layered clad material or of the surfacelayer of the two-layered clad composite material or by maintaining theCu amount and adding Pd or Pt.

The addition of Pd or Pt in the present invention may be replaced withthat of another platinum group element (Ru, Rh, Os, Ir) which producesthe same effect.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic perspective view showing an example ofthree-layered clad composite mineral in accordance with the presentinvention.

FIG. 2 is a schematic sectional view showing another example ofthree-layered clad composite material.

FIG. 3 is a schematic sectional view showing an example of two-layeredclad composite material in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The sliding contact material and the clad composite material inaccordance with the present invention show excellent performancesagainst the deposition thereby removing the deposition from thecommutator to the brush to depress the generation of the needle-likeabrasion powder while maintaining the excellent contact stability of theAuAg alloy. Naturally, the abrasion rate is decreased and the weldingresistance is elevated.

This brings epoch-making results that the starting voltage of the motorcan be maintained at a low level and even the extremely thin surfacelayer of the AuAg based alloy formed for minimizing the change with timepossesses an abrasion resistance. Moreover, the increase of the startingvoltage of the motor by the addition of Cu or the addition of Pd or Ptis within the permissible range.

The deposition from the alloy to the brush can be removed to depress thegeneration of the needle-like abrasion powder by increasing the amountof Cu in the AgCu alloy or the AgCuNi alloy mainly taking charge of theelevation of the abrasion resistance or adding Pd or Pt.

Naturally, the abrasion rate is decreased and a remarkably longer lifecompared with that of conventional material can be realized.

The increase of the starting voltage of the motor by means of theincrease of the Cu amount or the addition of Pd or Pt is within thepermissible range.

The reasons why the compositions are restricted in claims 1 to 8 are asfollows.

AuAgCu Alloy

The AuAgCu alloy is one in which its abrasion resistance is elevatedwhile maintain its contact resistance and anti-sulfur performance bymeans of adding a small amount of Cu to a conventional AuAg alloy.

Accordingly, if the Ag content is below 10% in weight, the hardness isso low that the adhesive wear is likely to occur. On the other hand, ifthe Ag content is over 60% in weight, especially the anti-sulfurperformance becomes inferior to deteriorate the performances with time.If the Cu content is below 0.1% in weight, no effects of elevating theabrasion resistance are produced, and if it is over 7% in weight, thecontact resistance becomes larger to elevate the starting voltage whenit is incorporated in a motor.

It is most effective that the Ag content is adjusted to be 30 to 50% inweight, the addition of Cu is adjusted to be 3 to 6% in weight and thebalance is Au.

AuAgPdCu Alloy

The AuAgPdCu alloy is one in which its abrasion resistance is furtherelevated while maintaining its contact resistance and anti-sulfurperformance by means of adding a small amount of Pd to the AuAgCu alloy.

Accordingly, the addition effects of Ag and Cu are the same as those ofthe AuAgCu alloy, and if the Pd content is below 0.1% in weight, noeffects of adding Pd to the AuAgCu alloy are produced, and if it is over7% in weight, the black powder is easily produced to make its contactresistance unstable.

It is most effective that the Ag content is adjusted to be 30 to 50% inweight, the addition of Cu is adjusted to be 3 to 6% in weight, theaddition of Pd is adjusted to be 0.5 to 3% in weight and the balance isAu.

PtAuAgCu Alloy

The PtAuAgCu alloy is one in which its abrasion resistance is furtherelevated while maintaining its contact resistance and anti-sulfurperformance by means of adding a small amount of Pt to the AuAgCu alloy.

Accordingly, the addition effects of Ag and CU are the same as those ofthe AuAgCu alloy, and if the Pt content is below 0.1% in weight, noeffects of adding Pt to the AuAgCu alloy are produced, and if it is over7% in weight, the black powder is easily produced to make its contactresistance unstable.

It is most effective that the Ag content is adjusted to be 30 to 50% inweight, the addition of Cu is adjusted to be 3 to 6% in weight, theaddition of Pt is adjusted to be 0.5 to 3% in weight and the balance isAu.

AgCuNi Alloy

The AgCuNi alloy is one in which its abrasion resistance is elevated bymeans of adding a larger amount of Cu compared with that of theconventional AgCuNi alloy.

Accordingly, if the Cu content is below 5% in width, the Cu content isinsufficient and adhesive wear is likely to occur as the conventionalalloy, and if Cu content is over 10% in weight, the contact resistancebecomes larger to elevate the starting voltage. If the Ni content isbelow 0.1% in weight, the mechanical performances, especially theelevation of hardness cannot be obtained, and if it is over 1% inweight, the instability of the contact resistance due to oxidation of Niand the problem regarding its processability remain.

It is most effective that the Cu content is adjusted to be 8 to 10% inweight, the Ni content is adjusted to 0.3 to 0.5% in weight and thebalance is Ag.

AgPdCu Alloy and AgPdCuNi Alloy

The AgPdCu alloy and the AgPdCuNi alloy are alloys in which therespective abrasion resistances are elevated while maintaining theircontact resistances and anti-sulfur performances by means of addingsmall amounts of Pd to the conventional AgCu alloy and AgCuNi alloy.

Accordingly, if the Pd addition is below 0.1% in weight, no effects ofadding Pd to the AuCu alloy and the AgCuNi alloy are produced, and if itis over 1.5% in weight, the black powder is easily produced to make itscontact resistance unstable.

If the Cu content is below 3% in weight, addition effects are seldomproduced and the adhesive wear is likely to occur, and if it is over 10%in weight, the contact resistance becomes larger to elevate the startingvoltage.

If the Ni content in the AgPdCuNi alloy is below 0.1% in weight, themechanical performances, especially the elevation of hardness can bescarcely obtained, and if it is over 1% in weight, the instability ofthe contact resistance due to oxidation of Ni and the problem regardingits processability renain.

It is most effective that the Pd addition is adjusted to be 0.3 to 1% inweight, the Cu content is adjusted to be 3 to 5% in weight and thebalance is Ag in the AgPdCu alloy, and that the Pd addition is adjustedto be 0.3 to 1% in weight, the Cu content is adjusted to be 3 to 5% inweight, the Ni content is adjusted to be 0.3 to 0.5% in weight and thebalance is Ag in the AgPdCuNi alloy.

PtAgCu Alloy and PtAgCuNi Alloy

The PtAgCu alloy and the PtAgCuNi alloy are alloys in which therespective abrasion resistances are elevated while maintaining theircontact resistances and anti-sulfur performances by means of addingsmall amounts of Pt to the conventional AgCu alloy and AgCuNi alloy.

Accordingly, if the Pt addition is below 0.1% in weight, no effects ofadding Pt to the AuCu alloy and the AgCuNi alloy are produced, and if itis over 1.5% in weight, the black powder is easily produced to make itscontact resistance unstable.

If the Cu content is below 3% in weight, no addition effects areproduced and the adhesive wear is likely to occur, and if it is over 10%in weight, the contact resistance becomes larger to elevate the startingvoltage.

If the Ni content in the PtAgCuNi alloy is below 0.1% in weight, themechanical performances, especially the elevation of hardness can bescarcely obtained, and if it is over 1% in weight, the instability ofthe contact resistance due to oxidation of Ni and the problem regardingits processability remain.

It is most effective that the Pt addition is adjusted to be 0.3 to 1% inweight, the Cu content is adjusted to be 3 to 5% in weight and thebalance is Ag in the PtAgCu alloy, and that the Pt addition is adjustedto be 0.3 to 1% in weight, the Cu content is adjusted to be 3 to 5% inweight, the Ni content is adjusted to be 0.3 to 0.5% in weight and thebalance is Ag in the PtAgCuNi alloy.

The same effects of those of adding Pd or Pt can be obtained by theaddition of one or more other platinum group elements (Ru, Rh, Os, Ir).

In the AuAgCu alloy claimed in claim 1, the said alloy includes a solidsolution alloy as well as an AuAgCu alloy which is prepared inaccordance with the description disclosed in Japanese patent laid opengazette No. 6-260255 by diffusing Ag and Cu into Au (diffused materialof Ag and Cu to Au) which produces the same effect.

Also in the AuAgPdCu alloy claimed in claim 2 and the PtAuAgCu alloyclaimed in claim 3, the same effects produced by the solid solutionalloy can be obtained in the diffused material.

The present invention may be effectively applicable to all the slidingcontacts including those for a slip ring and a connector as well as forthe commutator for the direct current compact motor.

Several examples of the clad composite materials are shown in attacheddrawings. FIG. 1 is a perspective view showing an example of tape-likethree-layered clad composite material in which the clad compositematerial 1 is composed of a base layer 2 having a concave section and,an intermediate layer 3 and a surface layer 4 located in the concavegroove.

FIG. 2 is a sectional view showing an alternative example of the cladcomposite material of FIG. 1. In FIG. 2, an intermediate layer 3' has aconcave section and the both ends of which are exposed.

FIG. 3 is a schematic sectional view showing an example of two-layeredclad composite material. In FIG. 3, clad composite material 1' iscomposed of a base layer 2 having a concave section and a surface layer4'.

EXAMPLES

Although Examples of the present invention will be illustrated, theseare not construed to restrict the invention. In these Examples, "%" ofelements is % in weight unless indicated to the contrary.

Example 1

Tape-like clad material was obtained by joining an Au--Ag(35%)-Cu(5%)alloy to be employed as a surface layer to the surface of anAg--Pd(1%)-Cu(4)-Ni(0.5%) tape-like alloy to be employed as anintermediate layer. This joined material was inlay-joined to aCu--Sn(2.3%)-Ni(9.5%) alloy to be employed as a base layer to obtainclad composite material. Tis clad composite material was thermallytreated at 750° C. and rolled three times to obtain three-layered cladcomposite material having a total thickness of 0.3 mm and a width of 19mm composed of the surface layer having a thickness of 5 μm, theintermediate layer having a thickness of 20 μm and a base layer.

This clad composite material was processed to a triple-pole commutatorhaving an outer diameter of 3.3 mm and a length of 2.4 mm which was thenincorporated in a direct current compact motor for a compact diskspindle.

Test conditions were as follows:

Test Temperature:70° C.

Humidity:5% RH

Test Time:96 hours

Load:Actual compact disk

Rotation Mode:One starting and one stop were included per one hour

Rotation Speed:500 rpm

Brush Material:Ag--Pd(50%)

Contact Load:2 gf

Number of Test Motors:10

Upon the completion of the test, the number of the motors the operationof which were made impossible due to the conduction between thecommutators produced by needle-like abrasion powder or the like wasinvestigated, the starting voltages of the motors which at the time ofthe investigation could rotate were measured and the difference betweenthe voltages before and after the test was recorded as a startingvoltage difference. After the motors were dismantled, amounts ofabrasion powder and black powder deposited on the commutator and thebrush were examined and the number of needle-like abrasion powder wascounted. Then, an abrasion area of the commutator and its abrasion depthwere measured. These results were show in Table 1. Surface hardness ofthe commutator was recorded for reference.

The evaluation standard is as follows. This standard is unified in allthe tests.

    ______________________________________               ⊚                         ∘                                 .increment.                                         X    ______________________________________    Abrasion Powder,                 extremely small                             small   medium                                           large    Black Powder    Abrasion Area (μm.sup.2)                 0 ˜ 1000                             ˜1500                                     ˜3500                                           3500˜    Abrasion Depth (μm)                 0 ˜ 10                             ˜15                                     ˜25                                           25˜    Needle-like Abrasion                 extremely small                             small   medium                                           large    Powder    Contact Resistance (mΩ)                 0 ˜ 50                             ˜150                                     ˜350                                           350˜    Starting Voltage                 0 ˜ 0.1                             ˜0.2                                     ˜0.5                                           0.5˜    Change (V)    ______________________________________

"Alloy composition/alloy composition" and "alloy composition/alloycomposition/alloy composition" in Tables 1 to 5 means the respectivealloy compositions of two-layered clad composite material andthree-layered clad composite material, respectively, and marks "/"therein mean an interface between the surface layer and the base layerin the two-layered material and those between the surface layer and theintermediate layer and between the intermediate layer and the base layerin the three-layered material.

Example 2

Three-layered clad material consisting of a surface layer composed of anAu--Ag(37%)-Cu(3%) alloy (having a thickness of 5 μm), an intermediatelayer composed of an Ag--Pd(1.5%)-Cu(4%)-Ni(0.5%) alloy (having athickness of 20 μm) and a base layer composed of a Cu--Sn(2.3%)-Ni(9.5%)alloy was obtained in accordance with the procedures of Example 1, whichwas then incorporated in a motor. The test conditions were the same asthose of Example 1, and the results are shown in Table 1.

Example 3

Tape-like clad material was obtained by joining Au to be employed as asurface layer to the surface of an Ag--Cu(10%)-Ni(0.5%) tape-like alloyto be employed as an intermediate layer. This material was thermallytreated for diffusing the surface layer to alloy the surface layer whichwas then inlay-joined to a Cu--Sn(2.3%)-Ni(9.5%) alloy to be employed asa base layer to obtain clad composite material.

This clad composite material was thermally treated at 750° C. and rolledthree times to obtain three-layered clad composite material having atotal thickness of 0.3 mm and a width of 19 mm composed of the surfacelayer having a thickness of 5 μm, the intermediate layer having athickness of 20 μm and as base layer. The AuAgCu alloy of the surfacelayer (Au diffused material) at this time was analyzed by means ofelementary quantitative analysis with EPMA to contain 38.2% of Ag, 6.1%of Cu and a balance of Au.

The incorporation to the motor and the test conditions were the same asthose of Example 1 and the results are shown in Table 1.

Example 4

Clad material was obtained by inlay-joining a Cu--Sn(2.3%-Ni(9.5%) alloyto be employed as a surface layer to an Ag--Cn(6%)-Ni(0.5%) alloy to beemployed as a base layer.

This clad material was thermally treated at 750° C. and rolled threetimes to obtain two-layered clad composite material having a totalthickness of 0.3 mm and a width of 19 mm composed of the surface layerhaving a thickness of 20 μm and the base layer.

The incorporation to the motor and the test conditions were the same asthose of Example 1 and the results are shown in Table 1.

Examples 5 to 9

In accordance with the procedures of Example 4, five two-layered cladcomposite materials were obtained which had the respective surfacelayers composed of an Ag--Cu(8%)-Ni(0.5%) alloy (Example 5), anAg--Cu(10%)-Ni(0.5%) alloy (Example 6), an Ag--Pd(0.5%)-Cu(4%)-Ni(0.5%)alloy (Example 7), an Ag--Pd(1%)-Cu(4%)-Ni(0.5%) alloy (Example 8) andan Ag--Pd(1.5%)-Cu(4%)-Ni(0.5) alloy (Example 9) and the respective baselayers all composed of a Cu--Sn(2.3%)-Ni(9.5%) alloy.

The incorporation to the motor and the test conditions were the same asthose of Example 1 and the results are shown in Table 1.

Prior Example 1

Three-layered clad material consisting of a surface layer composed of anAu--Ag(40%) alloy (having a thickness of 2 μm), an intermediate layercomposed of an Ag--Cu(4%)-Ni(0.5%) alloy (having a thickness of 20 μm)and a base layer composed of a Cu--Sn(2.3%)-Ni(9.5%) alloy was obtainedin accordance with the procedures of Example 1.

The incorporation to the motor and the test conditions were the same asthose of Example 1 and the results are shown in Table 2.

Comparative Example 1

Two-layered clad material consisting of a surface layer composed of anAg--Cu(4%)-Ni(0.5%) alloy (having a thickness of 20 μm) and a base layercomposed of a Cu--Sn(2.3%)-Ni(9.5%) alloy was obtained in accordancewith the procedures of Example 4.

The incorporation to the motor and the test conditions were the same asthose of Example 1 and the results are shown in Table 2.

Comparative Example 2

Two-layered clad material consisting of a surface layer composed of anAg--Pd(3%)-Cu(4%)-Ni(0.5%) alloy (having a thickness of 20 μm) and abase layer composed of a Cu--Sn(2.3%)-Ni(9.5%) alloy was obtained inaccordance with the procedures of Example 4.

The incorporation to the motor and the test conditions were the same asthose of Example 1 and the results are shown in Table 2.

Examples 10 and 11 and Prior Example 2

Employing the same test conditions of Example 1 except that the testtime was made to be 500 hours, three clad composite materials having thesame materials as those of Example 3 (Example 10), of Example 1 (Example11) and of Prior Example 1 (Prior Example 2) were obtained and processedto commutator which were then incorporated in a direct current compactmotor for the above test.

The evaluation standard was conducted in accordance with that of Example1 though the test time was different and the results are shown in Table3.

Examples 12 and 13 and Prior Example 3

Employing the same test conditions of Example 1 except that the testtemperature was -30° C. and the test was made to be 500 hours, threeclad composite materials having the same materials as those of Example 3(Example 12), of Example 1 (Example 13) and of Prior Example 1 (PriorExample 3) were obtained and processed to commutator which were thenincorporated in a direct current compact motor for the above test.

The evaluation standard was conducted in accordance with that of Example1 though the test time was different and the results are shown in Table4.

Examples 14 to 18 and Comparative Examples 4 and 5

In accordance with the procedures of Example 1, seven three-layered cladcomposite materials were obtained which had the respective surfacelayers composed of an Au--Ag(37%)-Pd(0.5%)-Cu(3%) alloy (Example 14), anAu--Ag(37%)-Pd(5%)-Cu(3%) alloy (Example 15), anAu--Ag(35%)-Pd(0.5%)-Cu(5%) alloy (Example 16), anAu--Ag(35%)-Pd(5%)-Cu(5%) alloy (Example 17), aPt(5%)-Au--Ag(35%)-Cu(5%) alloy (Example 18), an Au--Ag(35%)-Cu(5%)alloy (Comparative Example 4) and an Au--Ag(40%)-Pd(5%) alloy(Comparative Example 5) and the respective intermediate layers allcomposed of a Ag--Pd(0.5%)-Cu(4%)-Ni(9.5%) alloy and the respective baselayers all composed of a Cu--Sn(2.3%)-Ni(9.5%) alloy.

Since the performances of these materials were elevated, the test timewas changed from 96 hours to 192 hours twice of the original time. Theincorporation in the motor and the test conditions were the same asthose of Example 1 except for the above test time and the results areshown in Table 5.

Example 19

In accordance with the procedures of Example 4, two-layered cladcomposite material was obtained which had a surface layer composed of aPt(0.5%)-Ag--Cu(4%)-Ni(0.5%) alloy and a base layer composed of aCu--Sn(2.3%)-Ni(9.5%) alloy. This was tested in accordance with the sameprocedures as those of Example 14, and the results are shown in Table 5.

As apparent from Tables 1 and 2, the abrasion performances including theabrasion powder and black powder, the abrasion area, the abrasion depthand the needle-like abrasion powder at the temperature of 70° C. and thetest time of 96 hours in Prior Example 1 were inferior. The needle-likeabrasion powder was generated in four motors out of 10 motors inComparative Example 1 and in 10 motors out of 10 motors in ComparativeExample 2 to fill the spaces between the commutators to conduct andshort-circuit the said commutators to stop the motors during the test.Especially, it is apparent from Comparative Example 2 that the blackpowder increased above the Pd content of 1.5% to produce the increase ofthe contact resistance and the starting voltage.

In Examples 1 to 9, the contact resistances and the starting voltageswere low and the abrasion areas and the abrasion depths exhibitedremarkably excellent results.

As apparent from Table 3 in which the evaluation was conducted at atemperature of 70° C. and a test hours of 500 hours, the excellentsliding performances were obtained in Example 10 and 11 in which nomotors stopped within 500 hours while all motors stopped within 500hours in Comparative Example 2.

As apparent from Table 4 in which the evaluation was conducted at atemperature of -30° C. and a test hours of 500 hours, the excellentsliding performances were obtained in Example 12 and 13 in which nomotors stopped within 500 hours while three motors out of 10 motorsstopped in Comparative Example 3.

Further, it is elucidated, as apparent from Table 5, that theimprovements in Examples 14 to 19 were more outstanding than those ofComparative Example 4. However, in Comparative Example 5 in which no Cuwas contained in the surface layer of the three-layered clad compositematerial, four motors out of 10 motors stopped. This means that theaddition of Cu to the AuAg alloy of the surface layer followed by thefurther addition of Pd is important, and the addition of only Pd withoutthe addition of Cu is not expected to produce sufficient effects.

                                      TABLE 1    __________________________________________________________________________    (Temperature: 70° C. Time; 96 hours)                       Abrasion       Needle-                                           Starting    Numerals in Hard-                   Number                       Powder,                            Abrasion                                 Abrasion                                      loke Voltage    Composition ness                   of Con-                       Black                            Area Depth                                      Abrasion                                           Change    is % in weight                (Hv)                   duction                       Powder                            (μm.sup.2)                                 (μm)                                      Powder                                           (V)    __________________________________________________________________________    Ex. 1       AuAg35Cu5/                108                   0   ◯˜Δ                            ⊚                                 ◯                                      ⊚                                           ⊚       AgPd1Cu4N10.5       CuSn2.3Ni9.5    Ex. 2       AuAg37Cu3/                110                   0   ◯                            Δ                                 ◯                                      ◯                                           ⊚       AgPd1.5Cu4Ni0.5/       CuSn2.3Ni9. 5    Ex. 3       Au(diffused                111                   0   ◯                            ⊚                                 ⊚                                      ⊚                                           ⊚       material)/       AgCu10Ni0.5/       CuSn2.3Ni9.5    Ex. 4       AgCu6Ni0.5/                115                   0   ◯                            Δ                                 ◯                                      ◯                                           ⊚       CuSn2.3N19.5    Ex. 5       AgCu8Ni0.5/                113                   0   ◯˜Δ                            ⊚                                 ⊚                                      ⊚                                           ⊚       CuSn2.3N19.5.    Ex. 6       AgCu10Ni0.5/                115                   0   ◯                            ⊚                                 ⊚                                      ⊚                                           ⊚       CuSn2.3Ni9.5    Ex. 7       AgPd0.5Cu4Ni0.5/                109                   0   ◯                            ⊚                                 ⊚                                      ⊚                                           ⊚       CuSn2.3Ni9.5    Ex. 8       AgPd1CulNi0.5/                101                   0   ◯                            ⊚                                 ⊚                                      ⊚                                           ⊚       CuSn2.3Ni9.5    Ex. 9       AgPd1.5Cu4Ni0.5/                101                   0   ◯                            ⊚                                 ⊚                                      ◯                                           ◯       CuSn2.3Ni9.5    __________________________________________________________________________

                                      TABLE 2    __________________________________________________________________________    (Temperature: 70° C. Time; 96 hours)                        Abrasion       Needle-                                            Starting    Numerals in  Hard-                    Number                        Powder,                             Abrasion                                  Abrasion                                       loke Voltage    Composition  ness                    of Con-                        Black                             Area Depth                                       Abrasion                                            Change    is % in weight                 (Hv)                    duction                        Powder                             (μm.sup.2)                                  (μm)                                       Powder                                            (V)    __________________________________________________________________________    Pri.        AuAg40/  110                    0   Δ                             X    X    X    ⊚    Ex. 1        AgCu4Ni0.5/        CuSn2.3Ni9.5    Comp        AgCu4Ni0.5/                 113                    4   Δ                             X    X    X    Δ    Ex. 1        CuSn2.3Ni9.5    Comp        AgPd3Cu4Ni0.5/                 104                    10  Δ˜X                             Δ                                  ◯                                       Δ˜X                                            X    Ex. 2        CuSn2.3Ni9.5    __________________________________________________________________________

                                      TABLE 3    __________________________________________________________________________    (Temperature 70° C., Time; 500 hours)                       Abrasion       Needle-                                           Starting    Numerals in Hard-                   Number                       Powder,                            Abrasion                                 Abrasion                                      loke Voltage    Composition ness                   of Con-                       Black                            Area Depth                                      Abrasion                                           Change    is % in weight                (Hv)                   duction                       Powder                            (μm.sup.2)                                 (μm)                                      Powder                                           (V)    __________________________________________________________________________    Ex. Au(diffused                111                   0   Δ                            Δ                                 ◯                                      ◯                                           ⊚    10  material)/        AgCu10Ni0.5/        CuSn2.3Ni9.5    Ex. AuAg35Cu5/                108                   0   Δ                            Δ                                 ◯                                      ◯                                           ⊚    11  AgPd1Cu4Ni0.5/        CuSn2.3Ni9.5    Pri.        AuAg40/ 110                   10  X    X    X    X    X    Ex.2        AgCu4Ni0.5/        CuSn2.3Ni9.5    __________________________________________________________________________

                                      TABLE 4    __________________________________________________________________________    (Temperature: -30° C., Time: 500 hours)                       Abrasion       Needle-                                           Starting    Numerals in Hard-                   Number                       Powder,                            Abrasion                                 Abrasion                                      loke Voltage    Composition ness                   of Con-                       Black                            Area Depth                                      Abrasion                                           Change    is % in weight                (Hv)                   duction                       Powder                            (μm.sup.2)                                 (μm)                                      Powder                                           (V)    __________________________________________________________________________    Ex. Au(diffused                111                   0   ◯                            ⊚                                 ⊚                                      ⊚                                           ◯    12  material)/        AgCu10Ni0.5/        CuSn2.3Ni9.5    Ex. AuAg35Cu5/                108                   0   ◯                            ⊚                                 ⊚                                      ⊚                                           ◯    13  AgPd1Cu4Ni0.5/        CuSn2.3Ni9.5    Pri.        AuAg40/ 110                   3   X    X    X    X    X    Ex.3        AgCu4Ni0.5/        CuSn2.3Ni9.5    __________________________________________________________________________

                                      TABLE 5    __________________________________________________________________________    (Temperature: 70° C. Time; 192 hours)                        Abrasion       Needle-                                            Starting    Numerals in  Hard-                    Number                        Powder,                             Abrasion                                  Abrasion                                       loke Voltage    Composition  ness                    of Con-                        Black                             Area Depth                                       Abrasion                                            Change    is % in weight                 (Hv)                    duction                        Powder                             (μm.sup.2)                                  (μm)                                       Powder                                            (V)    __________________________________________________________________________    Ex. AuAg37Pd0.5Cu3/                 108                    0   ◯˜Δ                             Δ                                  ⊚                                       ◯                                            ⊚    14  AgPd0.5Cu4Ni0.5/        CuSn2.3Ni9.5    Ex. AuAg37Pd5Cu3/                 106                    0   Δ                             Δ                                  ◯                                       Δ                                            ⊚    15  AgPd0.5Cu4Ni0.5/        CuSn2.3Ni9.5    Ex. AuAg35Pd0.5Cu5/                 117                    0   ◯                             ◯                                  ⊚                                       ⊚                                            ⊚    16  AgPd0.5Cu4Ni0.5/        CuSn2.3Ni9.5    Ex. AuAg35Pd5Cu5/                 106                    0   ◯                             Δ                                  ⊚                                       ⊚                                            ⊚    17  AgPd0.5Cu4Ni0.5/        CuSn2.3Ni9.5    Ex. Pt5AuAg35Cu5/                 160                    0   ◯                             Δ                                  ⊚                                       ⊚                                            ⊚    18  AgPd1Cu4Ni0.5/        CuSn2.3Ni9.5    Ex. Pt0.5AgCu4Ni0.5/                 141                    0   ◯                             ⊚                                  ⊚                                       ⊚                                            ⊚    19  CuSn2.3Ni9.5    Comp        AuAg35Cu5/                 108                    0   ◯˜Δ                             Δ                                  ◯                                       ◯                                            ⊚    Ex. 4        AgPd0.5Cu4Ni0.5/        CuSn2.3Ni9.5    Comp        AuAg40Pd5/                  96                    4   Δ˜X                             X    Δ                                       X    ⊚    Ex. 5        AgPd0.5Cu4Ni0.5/        CuSn2.3Ni9.5    __________________________________________________________________________

We claim:
 1. A sliding contact comprising an alloy comprising 0.1 to 1.5wt. % palladium, 3 to 10 wt. % copper and the balance being silver andfurther comprising 0.1 to 1 wt. % nickel.
 2. The sliding contact ofclaim 1 comprising a two-layered composite, said composite comprising asurface layer comprised of said alloy and a base layer comprised ofcopper or a copper-containing alloy.
 3. A three-layered compositecomprising:(1) a surface layer comprised of an alloy selected from thegroup consisting of:(i) 10 to 60 wt. % silver, 0.1 to 7 wt. % copper andthe balance being gold: (ii) 10 to 60 wt. % silver, 0.1 to 7 wt. %palladium, 0.1 to 7 wt. % copper and the balance being gold; and (iii)10 to 60 wt. % silver, 0.1 to 7 wt. % platinum, 0.1 to 7 wt. % copperand the balance being gold; (2) an intermediate layer comprised of analloy selected from the group consisting of:(i) 0.1 to 1.5 wt. %palladium, 3 to 10 wt. % copper and the balance being silver; (ii) 0.1to 1.5 wt. % platinum, 3 to 10 wt. % copper and the balance beingsilver; (iii) 0.1 to 1.5 wt. % palladium, 3 to 10 wt. % copper, 0.1 to 1wt. % nickel and the balance being silver; (iv) 0.1 to 1.5 wt. %platinum, 3 to 10 wt. % copper, 0.1 to 1 wt. % nickel and the balancebeing silver; and (v) 5 to 10 wt. % copper, 0.1 to 1 wt. % nickel andthe balance being silver; and (3) a base layer comprised of copper or acopper containing alloy.
 4. The three-layered composite of claim 3wherein:(1) the surface layer comprises alloy (i); and (2) theintermediate layer comprises alloy (i) or (ii).
 5. The three-layeredcomposite of claim 3 wherein:(1) the surface layer comprises alloy (i);and (2) the intermediate layer comprises alloy (iii).
 6. Thethree-layered composite of claim 3 wherein:(1) the surface layercomprises alloy (i); and (2) the intermediate layer comprises alloy(iv).
 7. The three-layered composite of claim 3 wherein:(1) the surfacelayer comprises alloy (i); and (2) the intermediate layer comprisesalloy (v).
 8. The three-layered composite of claim 3 wherein:(1) thesurface layer comprises alloy (i); and (2) the intermediate layercomprises alloy (i) or (ii).
 9. The three-layered composite of claim 3wherein:(1) the surface layer comprises alloy (ii); and (2) theintermediate layer comprises alloy (iii).
 10. The three-layeredcomposite of claim 3 wherein:(1) the surface layer comprises alloy (ii);and (2) the intermediate layer comprises alloy (iv).
 11. Thethree-layered composite of claim 3 wherein:(1) the surface layercomprises alloy (ii); and (2) the intermediate layer comprises alloy(v).
 12. The three-layered composite of claim 3 wherein:(1) the surfacelayer comprises alloy (iii); and (2) the intermediate layer comprisesalloy (i) or (ii).
 13. The three-layered composite of claim 3wherein:(1) the surface layer comprises alloy (iii); and (2) theintermediate layer comprises alloy (iii).
 14. The three-layeredcomposite of claim 3 wherein:(1) the surface layer comprises alloy(iii); and (2) the intermediate layer comprises alloy (iv).
 15. Thethree-layered composite of claim 3 wherein:(1) the surface layercomprises alloy (iii); and (2) the intermediate layer comprises alloy(v).
 16. A direct current motor comprising a commutator comprising thethree-layered composite of claim
 5. 17. A direct current motorcomprising a commutator comprising the three-layered composite of claim9.